1. Field of the Invention
The present invention relates to a recording material utilizing the heat sensitivity of a diazonium salt compound. More particularly, the present invention relates to a novel diazo heat-sensitive recording material developing red to magenta to violet, excellent in image storability and image fixing property.
2. Description of the Related Art
A diazonium salt compound has been used for a long time as a light recording material represented by diazo copy, and further, also applied recently for a recording material for which fixing of an image is required by utilizing a property that it is decomposed to lose function by the action of a light, and there has been suggested as a representative material a light fixing type heat-sensitive recording material by which a diazonium salt compound an a coupler are heated according to an image signal to be reacted to form an image, then the image is fixed by irradiation with a light (Koji Safuji, IMAGE ELECTRON INSTITUTE BOOK, vol. 11, pp. 290 to 296 (1982).
Further, there has been technical development of a diazonium salt compound such as improvement in storability and the like, and application to a full color heat-sensitive recording material has been reported (ELECTROPHOTOGRAPHY INSTITUTE BOOK, vol 26, pp. 115 to 125 (1987), FUJIFILM Research & Development, vol. 40, p. 13 (1995), Japanese Patent Application Publication (JP-B) No. 4-10,879 and the like).
In a lot of investigations for producing a full color sensitive material, magenta pigments are produced by using diazo compound having maximum absorption near 365nm. However, with increase of the abilities of a heat-sensitive recording material, it has been found that design in which sharpness is enhanced by placing a magenta material having visual sensitivity on the top layer is effective. For this design, it is necessary to use a coupler by which a magenta pigment is formed using a diazonium salt compound which can be fixed at a wavelength around 420 nm.
As a magenta coupler which, in heating, reacts with a diazonium salt compound which can be fixed at a wavelength around 420 nm, and develops color, there was used a coupler such as 1-hydroxycumarin or the like which develops color by reacting with a diazonium salt compound having the maximum absorption around 365 nm in heating. However, in this case, a pigment exhibiting very broad and brownish color was formed disadvantageously, and a magenta material could not be formed even if the substituent on the mother nucleus was changed.
For the purpose of improving this problem, a novel diazonium salt has been suggested in Japanese Patent Application No. 9-152,414. Hue obtained from a 1-hydroxycumarin coupler has not been satisfactory though it has been improved as compared with that obtained from conventional type diazo compounds.